Textile dyeing processes typically involve applying a dye to the textile web, such as by ink jet systems, spray systems, gravure roll, slot die, rod coater, rotary screen curtain coater, air knife, brush or other suitable application system or technique, followed by heating and/or steaming of the dyed textile web to promote binding of the dye to the textile web. Following the steaming operation, the textile web may be washed, such as in a bath of water or other cleaning solution, to remove unbound and excess dye from the web. For example, in some washing processes the textile web is immersed in a cleaning bath where the cleaning solution (typically water) flows over the web to wash away unbound dye.
The washing sequence of such a conventional textile dyeing process is often a relatively slow process because it relies on the diffusion of unbound dye molecules in the matrix of the textile web to reach the surface of the textile where it can become entrained in the flow of cleaning solution. Additionally, washing the dyed textile in this manner may require multiple washings to remove a desired amount of unbound dye from the web.
The application of ultrasonic energy to a textile web in the course of textile processing is also known. For example, as described in U.S. Pat. No. 4,302,485 (Last et al.), ultrasonic treatment may be applied to a textile web while the web is immersed in a bath of dye solution or other treatment solution wherein the ultrasonic energy increases the penetration of the dye or other treatment solution into the web. However, such a process requires a substantial amount (e.g, the entire bath) of dye to be used compared to the amount of dye that is ultimately desired in the web.
There is a need, therefore, for a dyeing process that reduces the amount of dye that needs to be used in dyeing a textile web and/or more readily removes unbound dye from a web during processing without removing already bound dye.